I copied part of a post from the thread about Practical Sailor from thinwater below and put into this new thread because I feel this is good info and will be lost if just in the PS thread:

"Upcoming studies include chemicals vs joker valves and dehumidification. Also this tickler on propylene glycol for winterizing and why it is a often a bad idea.Sail Delmarva: It's Always the Joker "

I found this pretty interesting. I had never thought of the issue of veg oil etc floating on top of the holding tank interfering with air transfer and odors.

As my aft heads pump has be making noise I've been adding head lube to it till I can get around to replacing the pump (seems not really worth it to rebuild these things) and wonder how that effects the valve etc (will have to look up the compatibility)

I also have been sometimes putting that blue stuff in the bowl and leaving it there all week while gone. Maybe this is what is responsibly for the problem above with the pump.

One would think that products marketed to an industry for a specific use would be compatible with that use. But it looks that this isn't so and it is buyer beware.

Was a good article. As a professional water treater I had pretty much accepted that PG was just better for use most of the time (I can not remember the last customer that I came across who is using the EG). But it is pretty apparent that it isn't. I can not remember if I drained the potable strainer body after pumping that stuff though the system so I'll have to check the clear body on the unit. I am pretty sure I drained the plastic strainer for the engine intake, so I don't know why it didn't occur to me to do the same to the potable water one (stupid I guess).

I thought I read a post from Mainesail earlier in the season that the Walmart RV PG mix wasn't good for the rubber in the system because it had some EG in it. But from the charts this doesn't appear to be a problem at all. In fact other than the human toxicity the EG looks superior for boat use in all respects.

So far as I'm concerned I will consider using only the EG next year I figure if I flush the potable water well (I flush all 3 of my tanks in the spring so that is 150 gals though those little lines) to the point that I can not taste it there isn't any danger.

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jobless, houseless, clueless, living on a boat and cruising around somewhere